Adhesive coating for filters



Patented 7, 1939 I PATENT OFFICE ADHESIVE COATING FOB FILTERS Donald 0.Simpson, Newark, Ohio, minor, by

memo assignments, to

Owens-Corning Fiberglas Corporation, a corporation of Delaware NoDrawing. Application September 21, 1085, Serial No. 41,62!

9 Claims.

My invention relates to adhesive substances or compounds adapted forcoating filter bases. The invention is particularly adapted for use withimpingement types of air or gas filters which consis't essentially ofmeans for'breaking thefiow of air orother gas into fine streams The airor gas is thereby brought into intimate contact with suitably coatedsurfaces, the coating usually comprising a viscous substance. The dustor foreign particles in the air or gas impinge upon these Matted glassfibers surfaces and adhere thereto.

or glass wool may be noted as an example of a filter base of theimpingement type.

Ordinary oils have long been used as a surface coating for such filterbases, but such use pre- 1 sents definite disadvantages. or objections.The

011 must have suflicient fluidity to permit eflective capillary actionso that the oil will penetrate and wet the accumulating layers of .dustor foreign particlesas they are deposited,in such manner'that theaccumulating particles will adhere to the filter. It has thus been foundnecessary to use oils or materials having verylow viscosity. The

method in general use for treating the filter bases with such oil in themanufacture of air or gas filters, consists in dipping the material tobe coated. into a bath of the oil and then draining it.

The oil continues to drip from the material for an indefinite period oftime and often throughout the entire life of the filter, the drippingbeing especially pronounced at higher temperatures.

This is obviously an objectionable feature. It

necessitates the use of pans or other contrivances to catch the dripwhile the filter is in use, and is otherwise undesirable.

An object of my invention is to provide a viscous coating material forfilter bases which is free from the above-noted objections and which Iwill maintain a practically constant viscosity throughout the ratherwide temperature range within which air filters are ordinarily used.

Other objects of the invention will appear hereinafter. The presentapplication includes certain sub- J'ect-matter disclosed in my copendingapplication Serial Number 644,814, filed November 29-, 1932, now PatentNo. 2,068,202 dated January 19, 1937, Manufacture of glass wool, and isa continuation of said application as to all subject- '50 matter commonto both said applications.

' A coating material for filters which I have used with satisfactoryresults as a coating for filter bases consisting of glass wool and thelike, comprises a heavy oil -refined to a point where it is .65 freefrom odor and contains about 25% of wax.

This product has a low cold test so that it remains liquid or viscous ata low temperature. It

is sufficiently liquid or viscous to effectively catch and retain thedust from the air at a temper 'ature as low as 20 F. below zero. It canalso be 5 raised to a temperature of 125 F. or higher without becomingsuillciently liquid to run or drip. This adhesive material may beapplied to the glass wool or otherfilte'r base by an ordinary sprayingoperation and preferably while the ma- 10 terialsare hot or warm, asmore fully set forth in my copending application hereinbefore referredto.

A novel and improved type of adhesive coating material or compound whichI have discovered, 15 comprises a low viscosity oil combined withsuitable stifiening materials of water soluble soap,

such as the alkali soaps, in such a manner that its viscosity remainspractically constant throughout a wide temperature range. Thistemperature 20 may range from zero F. to about 200 F.

One example of such compound consists in the combination of a sodiumsoap with a light mineral oil. This compound or mixture is formed bymixing the soap with water to form an emul- 25 sion, adding the oil tothe emulsion and boiling it until the water is driven off. The boilingmay be done in an ordinary oil refining kettle or'other container. Thisleaves a mixture of the soap and oil which is of uniform consistency andfree from 30 clots or chunks of the soapy material. I havev found thatby the manufacturing method just described and the use of properproportions of soap and water, an adhesive material is developed whichwill remain in a solid condition or 35 state in which it will not drip,throughout said temperature range from zero F. to 200 F. At the sametime the oil is retained in the adhesive in such form that itscapillarity is not materially reduced and it is, therefore, operative towet the 40 accumulating layers of dust in a manner similar to that ofordinary oils.

Specific examples of sodium soaps which I have found to give verysatisfactory results in commercial use in making an adhesive coating 45material such as just described, are sodium stearate NaCrsHasOz, andsodium oleate NaC1aH13O2.

In the use of sodium stearate, the following formula may be employed:

, Pounds Sodium stearate NaCmI-IasOz 14 Steam cylinder oil 86 Water 100The preferred method of combining these ingredients is to add the sodiumstearate to the water to form an emulsion. The steam cylinder oil isthen added to the emulsion and the mixture heated to 400 F. and held atthis temperature until the water is all driven off.

Modifications may be resorted to within the spirit and scope of myinvention.

I claim:

1. An air filtering material comprising a fibrous refractory materialand an oily substance forming a coating for the fibers of said material,said substance consisting of a mixture of oil, water soluble alkalisoap, and wax having such properties and in such proportions that itwill not run at a temperature of 100 F. and will remain viscous attemperatures below zero F.

2. An air filter comprising a filter base and an adhesive compoundforming a coating for the filter base, said compound comprising a sodiumsoap and an oil compounded therewith, said oil and soap being of suchnature and proportions and so compounded that the adhesive will notchange materially in viscosity over a temperature range of from zero F.to 200 F.

3. An air filter comprising a filter base and a viscous coating materialfor coating the said filter base, said coating comprising a compound ofsodium soap and a light mineral oil.

4. An air filter comprising a filter base and a filter, adhesive coatingtherefor comprising soap in combination with an oil having asubstantially constant viscosity over a temperature of oil and a watersoluble alkali soap.

8. An air filter comprising a'porous filter base and a viscous coatingtherefor, said coating comprising a compound of sodium soap and a lightmineral oil, said coating having such characteristics that the oil willpenetrate and wet through the layers of dust as they accumulate 'on thecoating, and which coating will not drip or run at atmospherictemperatures.

9. An air filter comprising a porous filter base and an adhesive coatingtherefor comprising a compound of sodium stearate and oil.

DONALD C. SINIPSON.

- said coating comprising a mixture of an oil and

